ARC Centre of Excellence in Population Ageing Research Working Paper 2013/15 Model Risk, Mortality Heterogeneity and Implications for Solvency and Tail Risk. Michael Sherris and Qiming Zhou. Michael Sherris is Professor in the School of Risk and Actuarial Studies and Chief Investigator at the Centre of Excellence in Population Ageing Research (CEPAR), Australian School of Business at the University of New South Wales; E-mail: m.sherris@unsw.edu.au We are grateful to the Australian Research Council for generous financial support. This paper can be downloaded without charge from the ARC Centre of Excellence in Population Ageing Research Working Paper Series available at www.cepar.edu.au